Phone prefixes, country codes and area codes, explained

PrefixBook is a small reference site about the digits at the front of a phone number: the +1, the area code, the 011 you dial to leave the country, the 1 you sometimes need and sometimes do not. Type a number into the box at the top and the reader tells you what its prefix says about it, meaning the region, the time zone and a few flags such as toll-free or premium-rate. It does not tell you who the caller is, and I would be wary of any site that claims it can from ten digits alone.

Why a book about prefixes?

Because most phone confusion starts before the number begins. A call from a Jamaican line looks the same as one from Ohio. A contact saved with a leading zero will not connect from abroad. A hotel phone wants 9, then 1, then ten digits, and says nothing helpful when you get it wrong. Each of those problems has a short, boring explanation, and boring explanations are exactly what a reference book is for. I wrote this site so that I would stop answering the same questions by text message.

The site has two halves. One is the reader and the area code index, which cover the facts of a prefix: place, time zone, whether it is shared by several codes. The other is a short shelf of guides that explain how dialing works, written for people who want an answer and a reason in about five minutes of reading.

How to read a result

When you submit a number, the reader splits it into the parts the North American numbering plan defines: the three-digit area code, the three-digit exchange, and the four-digit line. It shows the international form of the number (the +1 version you can save in any phone), then what it knows about the area code. If the code is a regular US geographic one, you get the main places it serves and its time zone. If it belongs to Canada, a US territory or a Caribbean country, the result says so, because that is the detail that matters for what a call back costs.

Anything the digits cannot show is left out on purpose. There is no owner, no carrier and no line type, since those live in private records. If a result and your gut disagree, trust the gut and read the note under the result. The reader page explains each field one by one.

Situations we write about

The guides follow the questions people really have when they stare at a phone screen. Start with why numbers start with +1 if the plus sign has always looked like decoration to you. It explains that +1 is a shared code and not a country, which is the root of nearly everything else. If you are about to phone family overseas, dialing internationally with 011 or the plus sign lays out the pieces in order and shows what to do with a leading zero.

The question I get most from friends is when to dial 1 before the area code. The honest answer is that it depends on whether you are on a mobile or a landline, and on whether your region runs on overlays. Then there is the one that costs people money, calling Canada and the Caribbean, where the dialing looks domestic and the billing may not be. And for a rarer but nastier case, 900 numbers and other pay-per-call prefixes explains who pays when a prefix is built to charge the caller.

What the area code index is for

The index lists the geographic US area codes we hold, grouped by state, with their main cities and time zones. People use it in two ways. Some look up a code they have just seen on a missed call. Others browse, which is a perfectly good way to learn that a state can have a dozen codes and that big cities often have two or three layered on top of each other. Each code sits in its own row with its cities and time zone, so you can find it by state or by number.

A word of caution about location. An area code records where a number was first set up. People keep their numbers when they move, and mobile numbers have no fixed home at all. So a code from your own state is not a reason to trust a call, and a code from far away is not a reason to panic. It is one small fact among several.

What this site does not do

PrefixBook is independent. It has no tie to any carrier, to a government agency or to a people-search company, and it does not sell data. The reader keeps no account for you and sets no cookies. A number you type is used to build the result page for that single request and is not saved in a database, although the web server's standard logs hold the request for about a week, which the privacy page explains plainly.

It also does not rate callers. Labels such as "Scam Likely" or "Spam Risk" are guesses made by carriers and apps from patterns, and they are not verdicts. When we mention one, it is to tell you what it means and how far to trust it. If a call worries you, the dependable steps are dull ones: do not call back an unknown number, find the real number of the organisation on its own website, and report the call at reportfraud.ftc.gov.

Who writes this

Everything here is written and checked by one editor, Marit Holloway, who rereads each page against the original rule or agency page and puts a date on it. If you find a mistake, tell us through the contact page and corrections come first in the queue. More about the way we work is on the about page.